The Temuka Leader THURSDAY, MARCH 27, 1884. WHAT FARMERS OUGHT TO KNOW.

Temuka Leader, Issue 1157, 27 March 1884, Page 2

The Temuka Leader THURSDAY, MARCH 27, 1884. WHAT FARMERS OUGHT TO KNOW.

AGRICULTURAL CHEMISTRY. ( Written specially for this Paper.) vm. LIMINft LAND. In our last article we considered drainage, ploughing, and the respective benefits of deep and shallow ploughing. We now proceed to briefly glance at the chemical and mechanical changes wrought on land by manuring with lime. The effects of this manure are manifold. The following uses are mentioned : —lt warms the soil, for by union with water for which it has a great affinity, heat is liberated. Warmth we all know is required by seeds when germinating. When excess of organic matter is present in land, as in reclaiming a swamp, it destroys it. The heat evolved from the chemical union with water and carbonicacid is also destructive of organic matter. It also neutralises the sourness of acid grounds. Lime is the direct food of many plants. It is found in greatest abundance in the leguminosae —clover, pea, broom, gorse require large quantities. It combines with carbonic acid to form limestone, which in very fine division affords a good

manure, taking however a longer time to act. Lime is also used to get rid of insects when they infect land. It also induces porosity, and in this way it acts beneficially.

It is interesting to understand how lime effects the decomposition of organic matter in the soil. Organic substances, we have already seen, are composed to a great extent of hydrogen and oxygen. Lime, we know, has a great tendency to combine with water (hydrogen and oxygen). This oxide (lime being oxide of calcium) having such an affinity for hydrogen and oxygen, pulls, or drags out, so to speak, these elements of water present in organised substances, and when it unites with them, it combines to form hydrate of calcium, or slaked lime, the result being just the same as when water is poured on lime. In this way the oxide effects the destruction of organic matter. Not only is this negative good accomplished by lime, but a positive one also. Carbon, we have seen, is another important element in organic chemistry, and when this is liberated by the withdrawal of hydrogen and oxygen, it tends to form the compound carbonic acid, by union with oxygen. In this way it turns the noxious into not only the innoxious compound, but also into a most useful and necessary one. Peaty grounds are those which contain an excess of organic material ; a copious dose of lime is generally used to remedy the defect. In correcting sourness or acidity, the action of lime may be traced to its tendency to combine with acids to form salts. Thete terms have been already explained and we will not recur to them. Lime being a strong base or alkali, combines with whatever acid may be present in excess, chiefly organic ones, to form the corresponding salt. The salt is not acid to any great extent, and thus the sourness is destroyed, and the excess of acid removed. In this way lime neutralises, by combining with an acid and forming a neutral compound. It is unnecessary to remark that lime io part of the food of plants. Should there be a deficient quantity present in the soil, the addition of a little will, of course, benefit the crop. Swedes remove nearly 401bs of lime per aero of crop. Other classes of turnip remove different quantities, one ISlbs an acre, another 91 bs, another 6£lbs. One class of carrots removes 401bs of lime per acre. From these figures we see that lime is a very important inorganic constituent of soil, being an iudispensible component of many plants. It is laid down that lime should be applied to land in the slaked state. This is due to the fact that when slaked, lime is in a state of very fine division, and thus in the state best adapted for accomplishing its ends. But we . saw that lime destroys organic matter by 7 drawing from the decaying vegetable matter hydrogen aud oxygen to slake itself. When soil is manured with it for that purpose, applying it in the unslaked condition seems to be the natural method. In the case of slaked lime being put on land to destroy acidity, the acid will generally be stronger than the water and will force it out and take its place, thus it does not matter much whether the lime be slaked or not. This fertiliser has a great tendency to sink into the subsoil and below it, so that it should not be ploughed in deep. Lime may exist in soil in combination with various acids, as a silicate, as a phosphate, ns a carbonate, as a sulphate. In the last case it forms the insoluble gypsum, as a carbonate it is a limestone, and as a phosphate it forms bone material, and it may be either soluble or insoluble. The ordimv li ono phosphate of lime (Ca3,P04,2) is iiu-oluhie, and when bones are applied to land as manure the good results have to be waited a long time for ; the weathering action must have time to operate and make it soluble. When, however, the insoluble phosphate (C»3,P06,2) is, by the action of sulphuric acid (P 12,504) converted into the soluble one (CaH4,P04,2). In this way much time is saved in applying the superphosphate (CaH4,P06,2) or soluble one instead of the insoluble bone dust.

And yet another use of lime has to be noticed. Olay and soil we know consists of the bases, oxide of iron, oxide of magnesium, oxide of aluminium, oxide of potassium, oxide of sodium ; these bases or alkalies are united with one acid, silica, thus forming the various silicates of iron, magnesium, etc. Some of these silicates, however, are not very soluble in water, and are thus practically useless to plant growth. Lime is a very strong base, and is capable of, so to speak, driving the oxide of, say, potassium, out, and taking its place and uniting with the silica. By so doing it liberates the potash, which will combine with_ water, or carbonic acid or soma other acid, and will form a soluble compound. In this way lime performs a veiy great work, namely, by changing some useless constituents present in the soil to beneficial ones, and adapting them to the use of plants. From this summary of the uses of lime as a manure, it can be easily seen what a great work it accomplishes. In many cases its application proves beneficial, though there are already in the soil various compounds of itself. Whether this fertiliser should be applied in very heavy dressings at lengthened periods, or whether in small dressings at short intervals, has been a disputed question. The best authorities on the subject, bow ever, appear to be in favor of the latter course. One fact must be carefuMy borne in mind, namely, that lime is useless on land that is not properly drained. Lime on heavy soils induces porosity and looseness ; on light sandy soils it induces tenacity, Boening. This is a method for pulverishig stiff clays. Burning effects in a short time what the action of the weather would take a long time to accomplish. Its chief uses are, (1) to drive off as gases any excess of organic matter there may be present in the soil, (2) to render the unlocked store of plant food obtainable by the plant by changing in a very short time many insoluble into soluble compounds, (3) to bring about the pulverisation of the soil which results to some extent from the foregoing causes, (4) to destroy noxious weeds and in this way clean the soil.

Paring and burning as a means of improving land is little practised here, but when our land has become to a certain extent exhausted and requires renovation, doubtless every device will be resorted to and brought into action to restore the fertility of our worn out land. {To he Continued.)